Fluidized Bed Carbonitriding

Fluidized bed carbonitriding is a case hardening process. You introduce carbon and nitrogen into the workpiece surface simultaneously at elevated temperature in a fluidized bed of particles. The stuff diffuses in and makes the case hard and wear-resistant without needing extra quenching afterwards. If you want to weld afterwards, be careful: the hardened layer is brittle. You must grind or mill it off beforehand, otherwise the weld metal or heat-affected zone will crack. And don't weld directly on the layer; it can't take it.